Photochromic eyeglasses are eyeglasses which lenses are quickly colored in an outdoor irradiated with light containing UV rays such as sunlight to function as sunglasses and which are discolored in an indoor irradiated with no such light to function as ordinary transparent spectacles, and demands thereto grow larger in recent years.
As a method for producing plastic lenses having a photochromic property, various methods have been proposed. As one of these methods, there is known coating method, wherein a layer having a photochromic property (hereinafter, called photochromic coating layer) is formed on the surface of a plastic lens using a coating liquid containing a photochromic compound (hereinafter, called photochromic coating agent).
However, the photochromic coating agent has generally poor adhesion to the surface of a plastic lens substrate, so that a primer layer is formed on the surface of the lens substrate prior to forming the photochromic coating layer. As a resin for forming such a primer layer, a coating composition containing a moisture-curing polyurethane resin has been proposed (Patent Document 1).
On forming a primer layer or a photochromic layer by the coating method, the spin-coating method is generally employed. In the spin-coating method, while a lens substrate is spun around its central axis, a coating liquid is dropped onto the surface of the substrate, so that the coating liquid is spread by centrifugal force caused by spinning to form an uniform coating film.
The spin-coating method is a technique mainly employed for forming a resist film in photolithography of semiconductor wafers or forming a recoding film on a substrate for optical disks. Spin-coating apparatuses have, therefore, specification suitable to the materials of these films. There have been various proposals on spin-coating apparatuses in accordance with substrates to be coated or materials of coating films (Patent Document 2 and Patent Document 3).
The market size of photochromic eyeglass lenses is not so large at present, and there is no spin-coating apparatus specified for forming a primer layer or a photochromic layer on a lens substrate. In addition, there are quite few proposals on spin-coating apparatuses with special attention to producing photochromic eyeglass lenses, particularly for forming a primer layer. Under present circumstances, therefore, a general-purpose spin-coating apparatus, which is used for forming a resist film in photolithography of semiconductor wafers or forming a recoding film on a substrate for optical disks, is utilized for producing photochromic eyeglass lenses.    [Patent Document 1] Japanese Patent Laid-open Publication No. 261973/2004    [Patent Document 2] Japanese Patent Laid-open Publication No. 190532/2005    [Patent Document 3] Japanese Patent Laid-open Publication No. 23879/2001